Draft gear



1932- J. R. CARDWELL 4 4 DRAFT GEAR Filed Jan. 13, 1950 4 Sheets-Sheet 1 Feb. 9, 1932. J. R. CARDWELL 1,844,271

DRAFT GEAR Filed Jan. 13. 1930 4 Sheets-Sheet 2 Feb. 9, 1932. J. R. CARDWELL 1,844,271

DRAFT GEAR Filed Jan; 15. 1930 r 4 Sheets-Sheet 3 Feb. 9, 1932. J CARDWELL 1,844,271

DRAFT GEAR Filed Jan. 13, 1930 4 Sheets-Sheet 4 NZ I i Ewan Z Jams 75? C a/xwal Patented Feb. 9, 1932 nnrrsn stares earner entice JAMES R. CABDWELL, OF GHICAGQILLINOIS, ASSIGNOR TO CARDWELL WESTING- HOUSE COMPANY, A CORPORATION OF DELAWARE DRAFT GEAR.

Application filed il'anuary 13, 1930. Serial No. 420,688.

1; main constant irrespective of said wear.

Another object of the invention is the provision of new and improved means for releasing the parts of the draft gear and re turning the same to normal position after compression.

A still further object of the invention is the provision of new and improved pressure members for forcing the frictional elements into contact during compression of the gear.

1 Other objects of the invention are the provision of a new and improved draft gear that is simple in construction, cheap to manufacture, easily assembled, efiicient and reliable in operation, and one in which the frictional resistance to compression will not be affected by the wear of the friction elements.

(Ether and further objects and advantages of the invention will appear from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a plan view of the center sills of a railway car showing the lnvention 1n position therein, with parts in section and parts broken away Fig. 2 is avertical section of the gear;

Fig. 3 is a view similar to Fig. 1 with the parts in collapsed position;

Fig. i is a section on line 1t of Fig. 3;

3 Fig. 5 is a perspective view of one of the r friction plates;

Fig. 6 is a perspective view of one of the spring seats;

2 Fig. 7 is a perspective view of one of the 1; shoe engaging plates;

8 is a perspective view of one of the fulcrum blocks;

Fig. 9 is a diagrammatic view of the cam blocks in assembled relation; and

Figs. 10, 11 and 12 are diagrammatic views car each of which is provided with the draft 1 lug 11a and the buffer lug 12a.

Mounted between said lugs. is the draft gear which comprises a pair of casings or sleeves 13 and 14 within which is located two oppositely arranged groups of friction plates. Each group comprises two sets of intercalated plaltes 15 and 16 overlapping at their inner en s.

Follower blocks 17 and 18 are inserted between the lugs and draft gear. A draft yoke 19 secured to the coupler butt 21 embraces the gear as is usual in such constructions.

Suitable means are provided for forcing the friction plates into contact with each other during the compression of the gear. In the form of the device selected to illustrate one embodiment of the invention cam members are employed for this purpose. Sincethe arrangement at the ends of the gear is similar only one end need be described. Friction shoes 22 and 23 are arranged in frictional ,contact with the two groups of friction plates. These shoes are adapted to be forced outwardly against the friction plates by the cam blocks24 and 25 which engage suitable curved recesses 26 in said shoes. The opposite ends of the blocks are provided with curvedtoes or projections 27 for engaging theffulcrum block 29. The block 29 may, if desired,fbe

provided with inclined faces 28 although this is not necessary. The blocks 24: and 25 are also provided with intermediate curved surfaces 31 which are adapted to engage each other as at 82. j 7

If the force for compressing the gear be considered as always being applied along the center line of the gear, see Fig. 9, it can be readily proved that the curves of the contacting faces 31 of the cams 24: and 25 will be the same and both will be logarithmic spirals having the line 20, 20 as their common tan gent, for the chief property of this curve is that the tangent at any point always makes the same angle with its radius. If now we so construct the cams that the lines 32, 33 and 32, 34 are the radius vectors of these curves, it is evident that since the angles 20, 32, 33 and 20, 32, 34; or the angle 33, 32, 34 which, for convenience of description, will be termed the pressure angle, remain constant, the thrust on the shoes for any given force applied along the line 20,20 will remain constant irrespective of the amount of wear on the friction plates.

In actual practice, however, the force is not applied along the line 20, 20 but is ap plied at each side of said line, consequently the actual result will differ somewhat from the theoretical one unless provision be made for compensating for this application of the force. This may be accomplished by the use of the proper curves at 27. The equation for these curves will vary depending on the angle 'of the faces 28 which may vary from zero to any suitable angle, as will presently appear.

Thefollowing is a mathematical discussion of the problems involved and in which the equations for the different curves are derived.

Referring now to the diagrammatic View, shown in Figs. 10, 11 and 12, the letters A, A, are employed to designate a set of cam blocks 3 a member through which the force is applied, C the member resisting such force, and D the member for resisting the side thrusts of the members A, A.

The boundary curves of the movable blocks at 2, as shown. The blocks A and A are in contact (frictionless) at the point 4 their reactions T are normal to the boundary curve at 4c. The forces R- and T may be combined at the point 5 of intersection of the normals at '2 and l. The magnitude of T is determined from the fact that when the block A is in equilibrium the resultant W of T and R must i have the direction from 5 to the point 11 of intersection of the lines of action of the forces acting at points 7 and 9. The force at 9 must have the magnitude F, to balance the only other external force applied to A (considering those forces to be F and S at point 2) which have components in the direction of F C is 2F on the two blocks A and A, while the reaction of the wall D is X.

Let t be the angle from the line joining points 11 and 12, which we shall designate the line (11, 12) to the line (11, 5). Then the ratio of X to F is cot t.

(1) X/F=cot t.

We state now our main problem as follows.

ProbZewa-A variable force 2F is applied at B causing small translations and partial rotations of the blocks A and A, displacing blocks B, C and D, changing the points of contact 2, a, 7 and 9, and changing the magnitudes of S, R, T, *W and X. It is required to find the shape of the boundary curves of A in the neighborhoods of 2, 4t, 7 and 9 such that for small translations and rotations the ratio of X to F is constant.

In view of Equation (1) this problem becomes a purely geometric one which may be stated as follows.

Equivalent geometric problem.-Find shapes of curves in the vicinity of 2, l, 7 and 9 such that for small translations and rotations of A, in which the point of contact 4: moves along the line Z, the line (11, 5) remains parallel to its original position, where 11 is the point of intersection of the normals at 7 and 9, and 5 of the normals at 2 and 4.

In solving this geometric problem we need consider only one of the two symmetrically shaped blocks A and A, and the forces no longer need to be considered.

In Fig. 11 is represented block A before and after it has been moved. The new positions of points of contact with its boundaries are indicated by accents; thus 2 is the new point of contact of the block B with A. The boundary curves were not properly drawn since the line (11, 5) is not parallel tocthe line (11, 5) as it must be for a solution of our problem.

Let us take the boundary curve in the vicinity of points 7 and 9, a circle with center at point 11. Then the point 11" is the same point in the block as is the point 11. (Note that 5 and 5 cannot, therefore, be the same point in the block A, since there has been a rotation.)

Let us now translate the part of the figure carrying accented points so that point 11 comes into coincidence with point 11. Such a translation does not change the angles between lines. The line (11, 5) in its new position will be parallel to or coincident with (11, 5), if and only if it was either parallel to or coincident with it before the translation. This translation leads from Fig. 11 to Fig. 12 (the drawing is diagraimnatic only).

For the sake of simplicity, we shall determine the curves so that the line (11', 4) is parallel to (11, 4) in Figall which requires the lines to coincide in Fig. 12. Also we shall make the line (2, 5) perpendicular to (1 i In Fig. 12 a curve passing through points 2, 2", 4 4 is rotated about the fixed point 11, through an angle a, coming into a position passing through points 2', 4. In the figure'a is a negative angle, 0 is positive. If the line (11, 5) is used as a polar axis for polar coordinates, then the point (r, 6) goes into a point (r, 6+a) by the rotation. These conditions must hold for all small values of 0c (1) The tangents at 2 and 2 are parallel. (2) The tangents at 4 and 4 are parallel. (3) The point 4 lies on the line (11, 4). (4) The point (5) lies on the line (11, 5). In the following discussion we shall use the following.

T hemem I.The angle made by the radius vector to a point on a curve with the tangent at that point is not changed when the figure V is rotated about the pole.

The curve through point .4

Consider now the curve through the point 4 (a Let 4" (2", t) be a pointnear 4, and let the angle madewith the radius vector by the tangent at 4 be 1p and at 4" be 11/. Then from differential calculus tan,

When 4 is brought into coincidence with 4 by rotation of the figure it is seen that, by conditions (2) and Theorem I, =1//,,.

Hence is constant; call it 1/70; that is,

a E IC' The integral of this differential equation which satisfies the conditions, when and 1'=a is This curve is called a logarithmic spiral. It is a necessary and sufficient form for the curve through (4) satisfying conditions which we have imposed.

Since tan .,'=1/lc, we see that, in Fig 12 (2) h=tan ,8.

The curve through point Q Let ,I/ be the angle made by the tangent with i the radius vector at P, and be that angle at 2. Since the tangent line at 2 is parallel to the polar axis we see that =7r (l9+a).'-

Sinc the configuration at 2 comes from that at P by rotating that latter about the pole, it follows that =1r (6+a).

By difierential calculus tan \I/ =r Hence I I Let the polar coordinates of 5 and 5 be (:0, 0) and (w, (5) respectively. Since the lines (5, and (5, 4) are parallel, it follows that it x! At 4" we have r=a, s=qb a. Substitute these values in (2), the equation of the curve through 4 we find a a e Hence WVe have also, since the line (5, 2) is per pendicular to the line (11, 5),

The number m is expressible in terms of coordinates of the given point 2; thus m=r cos 0 Thus (4) defines on as a function of r, 0 and constants 112,10.

Hence the curve through 2' is the solution of where a is the function defined implicitly by (4).

From the theory of implicit functions it follows, after some calculations, that Equation (4) defines a as a single valued and analytic function of r, 6 in the vicinity of r=r 6 0, =a if andonly if 9 ,8.

Parametric equations of the curve throug /h 2 We wish to solve the equations i i i (4) a e 1" cos (6+a).

with the relation w=r cos 0 tan (6+a'),

Since a is small we may use it as a parameter in terms of which to express 1' and 0 by ISO use of power series. From (3) and (4) we We have V (1 2 (7) xe =r cos (0+a). COS a Let cos (6+a)=cos 0 'sin 0 (1+9 )a+ 0 0 +6 d+0g0t 1 cos 0,; 7=7"o+7"- a+7' a I .25 628111001 The conditions are satisfied. Then We Moreover h 1 ave kz z ks s (11) d7"=6Z0L[7" +27 a+37 oc a- I (9) e 1 +lm+ '2! 3! Hence for the left member of (6) we get,

(Z0 doc[6 +26 oc+3@ oc .1, from (9),

' 01: 1 And since 12) xe"d6=:rda [0 +(0 k+20 )0+ +26 k +30 )a Sin (6-1-11) =sin (6 +a For the right member of (6) we get, from =sin 6 cos a -l-cos 6 sin up and (11),-

(13) sin (6+oc) d7 6Za [1' sin 0 (21' sin G d-7 cos 6 (1+ 6 )a i 0 cos 0 sin 0,, 2

r +2r cos 0 (1 +0 311;, sin 0 01 Cos (9+oc)=COS (00+a cos 0 cos a sin 6 sin u 2 I 2 3 *2n cos 0o (1 1) 92 CO5 90 +8111 rz t 32:0 3T3 sin 0 216x0 where as a power series in a by multiplying the right p (1+6 +6 oz+0 oc member of (9) by as. For the right member of (7) we find from (8) and (10) 1' cos (6+a) =13, cos 0,, (r cos 0,,r sin 0 (1 +6 ))ac e, 2 7'2'COS 0 r, sin 0 (1 +0 +13, 6 sin 0 V n 2 i 1 cos6,,-r sin6,,(1+19 )+1" W l9 Si110 ])0z 13, and r i 1 Hence on equating likepowers of a in the i p) y two members of (7) We obtain COSap=1--,+ v

' w= cos 0 0 2 2( 1' 1) 3 i 1 -r-a --r' a 7' sin 0 6 -7- cos 0 =w7c' sin 6 2 I i 2 1' Sill 0,,0 r cos 0,, gs 7' sin 0 (1 0 +r g? cos 3 ys The first equation of (15) is satisfied, from Sm aP=aP 3 51 the definltion of 00. The first equatlon of (14-) 3 and thesecond of (15) serve to determine 60 1+0 1) 2 3 1) (16) 1 6 We have Qata -1 S111 6 0,

The left member of (7) may be expressed whence, since 1 cos 4%,

0 sin 0,, (17) 1 lcr cos 0 n, sin 6,,cos 0 1",, cos 6 +s1n 0 1", sin 0 cos 6,, 1*, (7c sin 6 cos 0,,+ sin 0,)

Equations After a long calculation we obtain The method we have followed can be used to determine as many of the constants 6,, m

as may be desired. We thus have the parametric equations of the desired curve:

The equations are worked outin" such a form, containing the parameters as, y and is,

with respect to point 11 and'line Z, and then find the curves in the vicinity of vpoints 4 and 2 to meet the conditions of the problem.

Suitable means are provided for resisting the inward movement of the shoes 22 and 23. As shown, the shoes are provided with shoulders against which shoe engaging plates 36 are adapted to engage. A resilient memher, as the spring 37, is interposed between these plates and is adapted to resist the movements of the shoes at one end of the gear toward those atthe other.

The fulcrum blocks 29 normally extend outwardly beyond the ends of the friction plates, whereby during the initial compression of the gear the block 29 will move inwardly, thereby forcing the shoes 22 and 23 laterally into frictional engagement with the friction plates before the ends of the same engage the follower blocks.

Resilient means such as the spring 38 is employed for yieldingly resisting'the inward movement of the fulcrum blocks 29 and the collapsing of the gear, in a manner that will now be described. The fulcrum blocks 29 are each provided with inwardly extending arms 39 which are adapted to embrace the plate 36 between the laterally extending lugs 42. The ends of the spring 38 engage spring seats or plates 41 which in turn engage the inner ends of the arms 39 of the fulcrum blocks 29. The plates 41 are each provided with inwardly extending projections 44 for positioning the spring 38. The plates 41 are each provided with an axial opening through which the spring 37, which is preferably arranged within the spring 38, extends and is held in position in the gear.

Suitable means are provided for. returning the parts to normal position after compression. The springs 37 and 38 are preferably utilized for this purpose. Retracting bars 45 are adapted to engagenotches 46 in the outer ends of the plates'15 and 16 at each edge thereof. The inner ends of the plates are reduced as at 47 for engaging between the bars 45' of the opposed set of plates. The pro ect1ons or lugs 42 onthe shoe engaging Lugs 48 on the sleeves 13 and 14 are adapted to be engaged by the retracting bars for returning the sleeves to normal position along with the other parts of the gear. The lugs 48 on the inner surface of the sleeves serve also as means for positioning the fulcrum blocks 29;

If desired, means maybe provided for holding the parts in assembled position for shipment, handling and the like. As shown,

a cylinder 51 having removable caps whichcarry bolts 52, is mounted within the springs axially of the gear, with the bolts 52 in engagement with a depressed portion 53 in each block 29, see Figs. 1 and 2. The cam blocks 2 and 23 are provided with suitable recesses for accommodating the bolts and the depressed portions 53 in the fulcrum blocks.

In the operation of the device, when force is applied tending to compress the gear, the followers 17 and 18 will first engage the fulcrum blocks 29, forcing the same inward against the tension of the spring 38, and at the same time, through the action of the cam blocks, the shoes are forced inwardly against the spring 37 and laterally outwardly, thus creating a transverse pressure on the friction plate-s.

Further movement results in the followers engaging the sleeves and fric tion plates to force the sameinwardly while in frictional contact with each other.

When compression is removed the spring 38 will move the fulcrum blocks 29 outward- 1y, thus relieving the pressure on the friction plates. The spring 37 will move the plate 36 outwardly, and with it the retracting bars 45, and through them the friction plates and sleeves. In actual practice, the spring seat 41 will engage the plate 36 and the combined'action of the springs 37 and 88 will promptly move the parts to normal position. By means ofthis arrangement, the release of the transverse. pressure on the friction plates is assured immediately after compression, and the prompt return of the parts of the gear to normal position is also assured.

This is a. continuation in part of my application Serial No. 1,820 filed Januar' 8, 1925, for patent on draft gear.

It is thought from the foregoing taken in connection with the accompanying drawings that the construction and operation of my device will be apparent to those skilled in the art, and that various changes in size, shape, proportion and details of construction may be made without departing from the spirit and scope of the appended claims.

' I claim as my invention 2 1. In a draft gear, a group of friction elements, means including a pair of friction sleeves open at each end for containing said elements, certain of said elements being movable with one of said sleeves, and certain of said elements being movable with the other sleeve, and means comprising toggle blocks normally extending beyond the outer ends of said sleeves for creating transverse pressure on said elements during compression of said gear, and means for returning the parts to normal position after compression.

2. In a draft gear, a pair of open-ended sleeves, a group of intercalated friction plates within said sleeves, means including rotatable cam and fulcrum blocks for creating transverse pressure on said plates during compression of said gear, said fulcrum blocks normally extending beyond the ends of said sleeves, and means to return the parts to normal position after compression.

3. In a draft gear, a pair of friction sleeves, friction elements in said sleeves, means including rotatable cam blocks for creating transverse pressure on said elements during compression of said gear, resilient means which, during its initial return movement, will release said cam blocks and during its final movement will exert pressure to return the parts to normal position.

4. In a friction gear, a pair of sleeves, intercalated friction plat-es within said sleeves, means including rotatable cam blocks for creating transverse pressure on said plates, fulcrum blocks for engaging said cam blocks,

and resilient means for engagingsaid fulcrum blocks for releasing the lateral pressure on said plates after compression.

5. In a draft gear, a pair of sleeves, a group of friction elements extending into both of said sleeves, rotatable cam blocks for engaging said elements, fulcrum blocks for engaging said cam blocks for creating transverse pressure on said elements during com pression of said gear, and resilient means for resisting the inward movement of said fulcrum blocks and cam blocks and for returning the parts to normal position after compression. V

6. A draft gear comprising a pair of sleeves, a group of intercalated plates frictionally engaging each other, within said sleeves, certain of said plates being movable with one of said sleeves and the remainder with the other sleeve, friction shoes in engagement with said group of plates, rotatable canimembers engaging said shoes, and fulcrum blocks for creating transverse pressure on said plates on compression of said gear, plates in engagement withsaid shoes, a spring between said plates, springseats inwardly'of saidv plates in engagement with said fulcrum blocks, and a spring engaging said seats.

7. In a draft gear, .a pair of casings, a groupof two sets of friction elements within said casingfor frictionally engaging each other, one group of said plates being movable with one of said sleeves and the other with the other sleeve, means including fulcrum blocks, rotatable cam members and friction shoes for creating transverse pressure on said elements at opposite ends thereof during compression of said gear, a spring for resisting the inward movement of said shoes, said spring on its initial release movement forcing-said blocks outwardly and on its final movement exerting pressure to return said elements to normal position.

8. Ina draft gear, a pair of sleeves, a group'of friction elements including friction shoes mounted within said sleeves, means including a fulcrum block and rotatable cam members for creating transverse pressure on said elements during compression of said gear, for causing them to frictionally engage each other, certain of said elements being movable with one of said sleeves and certain of said elements being movable with the other sleeve, a spring for resisting the inward movement of said blocks, and a spring for resisting the inward movement of said shoes, said first-named spring forcing said blocks outwardly during its initial release movement and on its final movement cooperating with said second-named spring for returning said elements to normal position.

9. In a draft gear, a group of intercalated plates, means to limit the lateral movement of said plates, friction shoes in engagement with said group of plates, plates engaging said shoes, a spring between said plates, means comprising rotatable cam and fulcrum blocks for creating transverse pressure on said shoes during compression of said gear, and spring seats in engagement with said fulcrum blocks, said seats being adapted to engage said shoe engaging plates for returning the parts to normal position after compression.

10. In a draft gear, a group of intercalated friction plates, a pair of easing members for containing said plates, means including rotatable cam members for creating transverse pressure on said plates at each end of said gear on compression thereof, and means for returning the parts to normal position after compression.

11. A draft gear comprising a plurality of relatively movable intercalated friction plates, casings for containing said plates, means including intercontacting toggle blocks for creating transverse pressure on said plates during compression of said gear, the contacting faces of said blocks being so curved that the point of contact will advance as the outer ends of said blocks move outwardly, and means for returning said parts to normal position after compression.

12. In a draft gear comprising a group of intercalated friction plates, a pair of retaining members for containing said plates, means including toggle members and fulcrum blocks for creating transverse pressure on said plates, and spring means engaging said fulcrum blocks for releasing the same after compression.

13. In combination, a pair of friction sleeves, a group of plates within said sleeves at each side of the axis thereof, a fulcrum block at each end of said gear and normally extending outwardly beyond the ends thereof, a pair of rotatable cam members in engagement with said blocks at each end of said gear, and means for yielclingly resisting the inward movement of said cam members during compression of said gear for creating transverse pressure on said plates, and resilient means for returning said blocks to normal position after compression.

14. A draft gear comprising a pair of openended sleeve members, friction elements within said sleeve members, certain of said elements being movable with one of said sleeves and the remaining elements with the other sleeve. means including toggle members for creating transverse pressure on said elements for forcing the same outwardly against said sleeve members during compression of said gear for resisting said compression, and means to return the parts to normal position after compression.

15. In a draft gear, a group of friction elements including friction shoes adapted to slide longitudinally of said ear, resilient means for resisting inward movement of said shoes, means including toggle members engaging said shoes for creating transverse pressure on said friction elements during compression of said gear, means for resisting said transverse pressure, and spring means for yieldine'ly resisting inward movement of said shoe engaging members, said spring means forcing said members outwardly during its initial release movement and on its final movement cooperating with said resilient means to return the parts to normal position.

16. In a draft gear, a group of relatively movable friction elements, means for limiting the lateral movement of said elements in one direction, and means for creating lateral pressure on said elements during the compression of said gear, said means including cam members having their contacting faces of such curvature that the lateral resultant of a force applied to the ends of said gear will remain constant irrespective of the wear on said elements, and means for resisting the compression of said gear and for returning the parts to normal position after compression.

17 In a draft gear, a group of relatively movable friction elements, means for limiting the lateral movement of said elements in one direction, means for yieldingly resisting the longitudinal inward movement of said elements and for creating lateral pressure thereon during the. compression of said gear, said means comprising toggle members having their contacting surfaces in the form of logarithmic spirals, and resilient means for returning the parts to normal position after compression.

In testimony whereof I affix my signature.

JAMES R. OARDWELL. 

